Identification of fragmented object outlines: A dynamic interplay between different component processes

The speed of fragmented picture identification depends on a large number of factors whose effects might change in time during an identification attempt. Using survival analysis and fixed fragmentation levels, previous research has shown that effects of complexity, fragment curvature, and time interact. Here, we study the effects of presentation duration and dynamic fragmentation levels. Fragmented object outlines were presented repetitively every 2.25 s, and at each presentation longer fragments were shown (possibly until closure). We recorded the lowest presentation number (minimum 1, maximum 10) that resulted in correct naming by the participants (N=84). Survival analysis was employed to investigate whether and when different factors like presentation duration, complexity, object category (natural vs. artifactual), symmetry, proximity, and fragment curvature influence correct identification. The results confirm and extend previous findings, and are interpreted within a dynamic, interactive processing framework.     

Rats’ visual-spatial working memory: New object choice accuracy as a function of number of objects in the study array

When rats had to find new (jackpot) objects for rewards from among previously sampled baited objects, increasing the number of objects in the sample (study) segment of a trial from 3 to 5 and then to 7 (Experiment 1) or from 3 to 6 and 9 (Experiments 2 and 3) or from 6 to 9 and 12 (Experiment 4) did not reduce rats’ test segment performance. Increasing study segment size improved test segment performance contrary the limited-capacity hypothesis concerning rats’ spatial working memory. This effect occurred when objects either differed visually (Experiments 1, 2, 4) or only by odor (Experiment 3). Rats performed no better than chance in finding a jackpot on their first choice from among three visually different objects in Experiments 1 and 2. Furthermore, results from Experiments 2 and 3 indicate that differences in the probability of finding a jackpot by chance in Experiment 1 were not responsible for failure to find the predicted inverse relationship. Results from Experiment 4 indicate that those from Experiments 2 and 3 were not solely due to size of test arrays. We discussed whether our findings could be attributed to innate foraging or perceptual isolation processes during testing or to perceptual encoding processes during exposure to study segment arrays.